When I was playing with my Research Districts for 3.0 mod, I felt that I had way too many empty, essentially useless building slots which I could only usefully fill by spamming fortresses. Frankly, I'd rather just have fewer building slots then have nothing to do with them, so I made a mod reducing max building slots from 12 to 8 (and changing FE initialization so they're not screwed): https://steamcommunity.com/sharedfiles/filedetails/?id=2465511922&searchtext=eight+building+slots
Tech costs for Stellaris have led to the bizarre phenomenon (especially pronounced since 2.6) where research gets quicker and quicker since costs scale way slower then your research income does. You can turn up tech costs, but that doesn't help much, since it makes the early game painfully slow (in my experience) and cripples unity as well. So I made a mod halving tier 1 costs, doubling tier 3 costs, tripling tier 4 costs, and quadrupling tier 5 costs. Tier 2 costs are unchanged. This makes things like (eg) cruisers, destroyers, autocannons, and plasma more useful, since in vanilla it takes very little time to get from these to battleships/XL weapons that blow them out of the water, so it isn't worth spending the research on them in most games. Now, you'll be spending a lot more time in the tier 2-3 zone, and thus the probability of war before you get battleships is much higher.
Tech costs for Stellaris have led to the bizarre phenomenon (especially pronounced since 2.6) where research gets quicker and quicker since costs scale way slower then your research income does. You can turn up tech costs, but that doesn't help much, since it makes the early game painfully slow (in my experience) and cripples unity as well. So I made a mod halving tier 1 costs, doubling tier 3 costs, tripling tier 4 costs, and quadrupling tier 5 costs. Tier 2 costs are unchanged. This makes things like (eg) cruisers, destroyers, autocannons, and plasma more useful, since in vanilla it takes very little time to get from these to battleships/XL weapons that blow them out of the water, so it isn't worth spending the research on them in most games. Now, you'll be spending a lot more time in the tier 2-3 zone, and thus the probability of war before you get battleships is much higher.